1. Field of the Invention
The present invention relates to an optical switching device capable of switching an electrical circuit from the switched-off state to the switched-on state by the irradiation of electromagnetic radiations (such as visible light, ultraviolet rays, infrared rays, X-rays and gamma-rays.
2. Description of the Prior Art
Photoelectric conversion devices having been hitherto widely used, capable of switching electric circuits from a switched-off state to a switched-on state by the irradiation of light or pulses of light include a photoconductive cell comprising a photoconductive material such as CdS and ZnO provided with ohmic contact electrodes, a p-n-p-n junction optical switch diode, etc. However, the former is disadvantageous in that the switching speed is as low as about 100 msec. On the other hand, it is the p-n-p-n optical switch diode that can bring about on-off action by utilizing photoelectromotive force caused by irradiating light on p-n junctions of a semiconductor device, and this can have a switching speed of from 0.05 to 0.10 .mu.sec.
However, once it is placed in the on state, the current continues to flow by the action of self-retension even when the irradiation of light is stopped. For returning it to the off state, it is necessary to decrease the circuit current by changing external conditions.
In addition to the above, there is recently produced on an experimental basis an optical switching device having the semiconductor hetero-structure super lattice structure provided with the long-period structure, comprising different kinds of semiconductors alternately laminated in layers (D.A.B. Millers, IEEE Journal of Quantum Electronics, 1985, Vol. QE-21, page 1462). It is impossible in such an optical switching device to switch an electric circuit in a high speed according to the irradiation/non-irradiation of light. However, the materials used for forming the above semiconductor hetero-structure supper lattice are limited to inorganic materials such a GaAs and Si, and also a complicated process is required for producing it. There has been no report on examples of optical-switching devices in which organic materials are used.